The invention was developed in connection with spreading aggregate onto a thin layer of liquid asphalt to produce a seal coat for an existing asphalt roadway. Its design has been influenced by the problems associated with that type of operation. However the spreader has been shown to work with other granular feed materials, such as asphalt pre-mix. Thus the term "aggregate", as used herein, is to be given a broad interpretation.
Historically, aggregate was hand shoveled from the truck box. More recently, detachable hopper-type spreaders have been commercially available, equipped with augers or rollers for laterally distributing and feeding the aggregate through gate-controlled slots. However, these prior art systems have commonly been characterized by several problems namely:
uneven feeding of the aggregate; PA1 dropping the aggregate from too high an elevation so that splashing of the asphalt away from the aggregate pebbles occurs; PA1 imperfect shut-off, with the result that aggregate can leak onto the roadway when not desired; and PA1 the inability to vary the width of the strip of aggregate laid down. PA1 the provision of the separately driven drum sections, coupled with separately operated closure flaps, enables the aggregate to be delivered in narrow strips or, alternatively, of full-box width; PA1 the underslung arrangement of the hopper brings it closer to the liquid asphalt (in the case of applying a seal coat) and reduces splashing; and PA1 the utilization of the ramp in conjunction with the feed drum assembly results in an even delivery of the aggregate.
The present invention was developed with the objective of providing a hopper spreader whose performance is improved with respect to these problems.